TY - JOUR
T1 - Abnormalities of mechanoreceptors in a rat model of neuropathic pain
T2 - Possible involvement in mediating mechanical allodynia
AU - Heung Sik Na, Sik Na
AU - Joong Woo Leem, Woo Leem
AU - Jin Mo Chung, Mo Chung
PY - 1993
Y1 - 1993
N2 - 1. Peripheral nerve injury sometimes leads to the development of neuropathic pain. One of the symptoms of such neuropathic pain is mechanical allodynia, pain in response to normally innocuous mechanical stimuli. We hypothesized that sympathetically driven dysfunction of cutaneous mechanoreceptors is responsible for signaling mechanical allodynia. The present study was undertaken to identify the types of sensory receptors that potentially mediate mechanical allodynia, with the use of a rat neuropathic pain model we have developed. 2. One week to 10 days after tight ligations of the L5 and L6 spinal nerves on one side, the rats fully developed behavioral signs of mechanical allodynia on the affected hindlimb. Various cutaneous mechanoreceptors originating from the neuropathic foot were examined by single-fiber recordings from the L4 dorsal root. 3. Although no particular abnormalities were found in other types of cutaneous mechanoreceptors, an unusual type of mechanoreceptor was found to be innervating the neuropathic foot. The response characteristics of this type of receptor resemble those of rapidly adapting mechanoreceptors (RAs), but with low and irregular static discharges during a maintained mechanical stimulus. We termed this unusual type as a 'modified rapidly adapting' mechanoreceptor (MRA). 4. The response characteristics of MRAs change to those of typical RAs after a systemic injection of phentolamine, an α- adrenergic receptor blocker. 5. We conclude that many RAs become abnormal under the influence of sympathetic efferents in neuropathic pain, so that their response patterns change to those of MRAs. We propose that this abnormality is responsible for signaling the mechanical allodynia that can be seen in neuropathic pain states such as causalgia.
AB - 1. Peripheral nerve injury sometimes leads to the development of neuropathic pain. One of the symptoms of such neuropathic pain is mechanical allodynia, pain in response to normally innocuous mechanical stimuli. We hypothesized that sympathetically driven dysfunction of cutaneous mechanoreceptors is responsible for signaling mechanical allodynia. The present study was undertaken to identify the types of sensory receptors that potentially mediate mechanical allodynia, with the use of a rat neuropathic pain model we have developed. 2. One week to 10 days after tight ligations of the L5 and L6 spinal nerves on one side, the rats fully developed behavioral signs of mechanical allodynia on the affected hindlimb. Various cutaneous mechanoreceptors originating from the neuropathic foot were examined by single-fiber recordings from the L4 dorsal root. 3. Although no particular abnormalities were found in other types of cutaneous mechanoreceptors, an unusual type of mechanoreceptor was found to be innervating the neuropathic foot. The response characteristics of this type of receptor resemble those of rapidly adapting mechanoreceptors (RAs), but with low and irregular static discharges during a maintained mechanical stimulus. We termed this unusual type as a 'modified rapidly adapting' mechanoreceptor (MRA). 4. The response characteristics of MRAs change to those of typical RAs after a systemic injection of phentolamine, an α- adrenergic receptor blocker. 5. We conclude that many RAs become abnormal under the influence of sympathetic efferents in neuropathic pain, so that their response patterns change to those of MRAs. We propose that this abnormality is responsible for signaling the mechanical allodynia that can be seen in neuropathic pain states such as causalgia.
UR - http://www.scopus.com/inward/record.url?scp=0027326893&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0027326893&partnerID=8YFLogxK
U2 - 10.1152/jn.1993.70.2.522
DO - 10.1152/jn.1993.70.2.522
M3 - Article
C2 - 8410153
AN - SCOPUS:0027326893
SN - 0022-3077
VL - 70
SP - 522
EP - 528
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 2
ER -